A coupling mechanism with the strength to fix a forcefully contracting muscle to a totally inert prosthesis, or to bone, would meet a serious and common need in clinical orthopaedics. We have explored a new approach to such a coupling. The hypothesis was that a coupling prosthesis with a low-mass, high-surface configuration designed to transfer force by shear would transfer greater loads, without pressure-damage to tissue, than can be transferred by the interlocking mechanism of sutures or staples. The resulting device is the OrthoCouplerTM. The Phase I feasibility study results exceeded expectations. This was a 60 day assessment reattaching 8 goat semitendinosus (hamstring) muscles;7 completed all testing - 6 with paired experimental/control data, one with experimental alone. Each proposed Aim was met:--devices were built, validated for cyclic fatigue life, implanted, and succeeded clinically. Excised specimens were 2.5 times the strength of an expertly applied state-of-the art-control (Krackow stitches under close direction of a senior orthopaedic oncologic surgeon). The proposed work applies the OrthoCoupler in goats to the most demanding setting imaginable - restablishing the knee extensor mechanism after complete excision of quadriceps tendon, patella, and patellar tendon, securing the cut quadriceps muscle stump to a tibial bone plate. This succeeded in four pilot animals - (servohydraulic testing to over 1000 N with femur fracturing without pullout). Specific Aim (1) assesses in a random block study the efficacy of two plausible improvements, each intended to facilitate ease of operative use compatible with minimally invasive placement, (2) standardizes design and fabrication with a contracted 'GMP'manufacturer and (3) rigorously reprises preclinical testing in a 'GLP'facility. Achieving these three specific aims would place the device at a decisive competitive advantage relative to any present alternative, and ensure our overriding long-term objective - commercialization of OrthoCoupler in a range of specific configurations for a market of over 20,000 muscle-to-prosthetic applications annually, including, but by no means limited to, orthopaedic oncology, revision arthroplasty, expanded tendon transfer and sports-injury reconstruction. PUBLIC HEALTH RELEVANCE: We have developed and patented a new technology for durable strong connections with tissue not having sufficient strength for conventional sutures or staples. A dominant need for this is in several orthopaedic dilemmas - sports injury reconstruction, orthopaedic oncology, revision joint replacement and tendon transfers. Pilot studies have succeeded in the most demanding application possible, reattachment of the body's most powerful muscle, the quadriceps femoris and the proposal will expand that work in an extended term goat model.